Abstract
Selective oxidation of benzyl alcohol to benzaldehyde was carried out with MoO2 nanoparticles (MoO2 NPs). MoO2 NPs were synthesized by two different approaches and characterized by several techniques. The synthesis was done by a hydrothermal procedure using ethylenediamine and either Fe2O3 or hydroquinone. In the latter case, an additional calcination step under N2 was performed to eliminate passivating agents at the surface of the nanoparticles. The synthesized nanocatalysts showed similar catalytic properties, being efficient catalysts in the oxidation of benzyl alcohol. High substrate conversion and product selectivity were achieved under all tested conditions. Studies were conducted using two different oxidants: tert-butyl hydroperoxide and hydrogen peroxide, in our continuous effort to obtain more efficient catalysts for more sustainable catalytic processes. When H2O2 was used as the oxidant, 94% yield was achieved with 100% selectivity for benzaldehyde, which was a very promising result to undergo other studies with this system. Moreover, to elucidate some aspects of the reaction mechanism, a study was conducted, and it was possible to conclude that the reaction undergoes, to some extent, through a radical mechanism with both oxidants.
Highlights
Molybdenum complexes are largely known for their good catalytic activity and have been widely used, especially in oxidation reactions, as homogeneous catalysts
In continuation continuation of of our our efforts efforts to to investigate investigate more more sustainable sustainable processes processes for for the the catalytic catalytic oxidation oxidation of several organic substrates, we report in this work the oxidation of benzyl alcohol catalyzed withwith two of several organic substrates, we report in this work the oxidation of benzyl alcohol catalyzed different typestypes of synthetized nanoparticles two different of synthetized nanoparticles
In the former case, synthesis hydroquinone as assisting agents, respectively [10]. In the former case, synthesis with Fe2 O3 working as an assisting agent has two roles: the first is to act as a nucleation seed for the with Fe2O3 working as an assisting agent has two roles: the first is to act as a nucleation seed for the growth of the MoO2 NPs; the second is a role as a regenerator of the oxidized EDA during the process
Summary
Molybdenum complexes are largely known for their good catalytic activity and have been widely used, especially in oxidation reactions, as homogeneous catalysts. The oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzCHO) is an important reaction because of the wide applications of the latter in industry [5]. The oxidation of benzyl alcohol to benzaldehyde continues to be studied, since this reaction has a high reactivity, but presents selectivity issues yielding some by-products, which are well-known [6]. In this context, both homogeneous and heterogeneous transition metal-based catalysts have been developed for aerobic alcohol oxidations [7]
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